四川盆地元坝气田长兴组古油藏的定量恢复及油源分析

目前虽认为元坝气田长兴组天然气主要为原油裂解气,但尚未进行该气田的古油藏的定量恢复并计算原油裂解气的资源量,并系统分析古油藏原油的来源.长兴组储层普遍可见固体沥青,是原油裂解的直接产物,且原油裂解在本区构造抬升变形前就已经完成,因此储层沥青可用来识别古油层的分布.根据储层沥青的纵向和平面分布,确定了7个可靠的古油藏和4个可能的古油藏,并运用容积法恢复出本区聚集的古原油为6.14×108 t,计算出相应的原油裂解气为3 807.08×108 m3,远大于现今气田的天然气探明储量,表明原油裂解气可以提供充足的气源,进一步证明了天然气主要为原油裂解气.通过长兴组储层沥青与不同层系烃源岩干酪根的碳同位素δ13C值对比,并结合烃源层分布和TOC等资料,确定古油藏原油主要来源于有机质类型以Ⅱ型为主的上二叠统吴家坪组烃源岩,其次为长兴组/大隆组烃源岩.后者主要分布在广元-南江-通江地区,该区的天然气勘探不能忽视该套烃源岩的生烃潜力与成藏贡献.      

南盘江盆地古油藏沥青地球化学特征及成因

南盘江地区生物礁古油藏的储层沥青主要分布在上二叠统和中上泥盆统。古油藏的储集层均为生物礁滩灰岩,沥青的主要储集空间以洞、缝为主,其次为基质孔隙和生物体腔内。南盘江古油藏沥青的成熟度很高, H／C原子比小于0．4,主要由残碳构成,这是沥青的非极性和极性抽提无抽提物的直接原因。在古油藏沥青地球化学特征研究的基础上,综合分析认为南盘江古油藏沥青主要源自泥盆系烃源岩,其次可能与下二叠统烃源岩有关。南盘江古油藏沥青与生物降解沥青和沉淀沥青质有很大的区别,其成因是油藏深埋时在高温、高压的作用下原油裂解成气后的焦沥青。     

Accumulation Mechanisms and Evolution History of the Giant Puguang Gas Field, Sichuan Basin, China

Solid bitumens were found throughout the carbonate reservoirs in the Puguang gas field,the largest gas field SO far found in marine carbonates in China,confirming that the Puguang gas field evolved from a paleo-oil reservoir.The fluid conduit system at the time of intensive oil accumulation in the field Was reconstructed,and petroleum migration pathways were modeled using a 3-D model and traced by geochemical parameters.The forward modeling and inversion tracing coincided with each other and both indicated that oils accumulated in the Puguang-Dongyuezhai structure originated from a generative kitchen to the northwest of the Puguang gas field.The deposition of organic-rich Upper Permian source rocks dominated by sapropelic organic matter in the Northeast Sichuan Basin, the development of fluid conduit system that was vertically near-source rock and laterally near-generative kitchen,and the focusing of oils originated from a large area of the generative kitchen,were the three requirements for the formation of the giant paleo-oil reservoir from which the giant Puguang gas field evolved.The Puguang gas field had experienced a three-stage evolution.The post-accumulation processes,especially the organic-inorganic interaction in the hydrocarbon-water-rock system,had not only profoundly altered the composition and characteristics of the petroleum fluids,but also obviously changed the physicochemical conditions in the reservoir and resulted in complicated precipitation and solution of carbonate minerals.     

Genetic link between Mississippi Valley-Type (MVT) Zn-Pb mineralization and hydrocarbon accumulation in the Nanmushu,northern margin of Sichuan Basin,SW China

The coexistence of Zn-Pb deposits and oil/gas reservoirs demonstrates that a close genetic link between them. The Nanmushu is a large Mississippi Valley-Type (MVT) Zn-Pb deposit discovered on the northern margin of the Yangtze block in recent years. The deposit is hosted in the Ediacaran Dengying Formation dolostone, accompanied by large amount of bitumen in the orebodies. The MVT Zn-Pb deposit overlaps with the paleo-oil/gas reservoir horizontally, and sandwiched in the paleo-oil/gas reservoirs at depth. The Cambrian Guojiaba Formation may have provided not only the oil for paleo-oil/gas reservoirs, but also ore metals for the Zn-Pb mineralization. With increasing burial depth, the Guojiaba Formation may have become more mature to form metal-rich fluids, and the metals migrated and accumulated with hydrocarbons to form a paleo-oil reservoir. Large-scale Zn-Pb mineralization may have occurred in the destruction process of paleo-gas reservoir. With the deep burial of paleo-oil reservoir, the paleo-oil reservoir may have transformed into a paleo-gas reservoir. Decoupling of metals and hydrocarbons during the paleo-gas reservoir formation may have provided the ore metals. Thermal sulfate reduction (TSR) during the paleo-oil/gas reservoirs formation may have provided the hydrogen sulfide for mineralization. Decompression and cooling during the paleo-gas reservoir destruction may have formed extensive metal sulfide precipitation and mineralization.     

四川盆地东北部气田海相碳酸盐岩储层固体沥青研究

川东北地区海相碳酸盐岩生物礁滩相储层中普遍存在着固体沥青.本文以普光气田上二叠统长兴组和下三叠统飞仙关组储层中固体沥青为研究对象,在显微镜下观察固体沥青的产状特征,测定固体沥青含量和计算固体沥青与储层孔隙的体积比率,分析固体沥青的成因及形成期次,推算古油藏的密度.普光气田飞仙关组固体沥青主要呈环边状附于鲕粒白云岩、残余鲕粒白云岩晶间溶孔,溶蚀孔壁,沥青含量在1.11%～5.73%之间,均值2.92%;长兴组生物礁储层固体沥青多呈团块状充填于各种溶蚀孔洞中,沥青含量0.31%～11.72%之间,均值3.57%.两套储层中的固体沥青含量都有随埋深而减少的趋势.飞仙关组储层中固体沥青与储层孔隙的体积比约为22%,长兴组为43%～56%.普光气田储层固体沥青为热演化成因并为两期形成,飞仙关储层固体沥青为轻质油古油藏裂解形成,长兴组储层固体沥青为稠油古油藏裂解形成.     

南盘江盆地油气成藏过程及天然气勘探前景分析

本文采用多种研究手段探讨了南盘江盆地的多期成藏、破坏过程。根据有机质成油、成气和油成气的化学动力学模型,计算了南盘江盆地主要烃源岩的油气演化过程;并通过对沥青充填期次、包裹体研究和胶结物期次与沥青的关系,研究了古油藏经历的多期次充注、破坏过程,据此初步建立了南盘江盆地古油藏演化模式。从南盘江盆地古油藏演化过程来看,南盘江盆地油气勘探应以原油裂解的天然气为主,但是由于该地区具有聚气早、破坏时间长的特征,尤其是三叠系沉积之后的巨厚剥蚀使原油裂解气保存的可能性变小,因此在该地区形成大中型天然气藏的难度很大,天然气勘探前景需要进一步研究。     

利用油包裹体丰度识别古油藏和限定成藏方式

储集层中残留烃类数量指示了它在地质历史中的古含油饱和度,它包括赋存于孔隙和裂隙之中的烃类和胶结物中的烃类流体包裹体,目前采用的分析技术有储层可溶烃数量和成分(抽提、TLC-FID、HPLC、ROCK-EVAL),油包裹体丰度(含油包裹体颗粒指数GOI,荧光颗粒定量QGF)、储层固体沥青数量(SBI)与流体包裹体地层学(FIS)。利用油包裹体丰度可识别古油藏,判识古油水界面(POWC),寻找再运移石油,确定天然气或凝析气藏早期是否有石油充注事件,识别次生油藏,寻找下伏油藏,限定油气充注模式。本文以塔里木盆地牙哈凝析气气藏与英南2气藏为例,展示了如何利用油包裹体丰度识别古油藏和限定成藏方式。     

川西坳陷中段上三叠统须家河组二段原油裂解成因天然气发现及成藏模式初探

川西坳陷中段具备多套烃源层、多个烃源区、多期油气生成、多期油气成藏同时又经历了多个构造期调整和破坏,纵向上发育的多套生储盖组合孕育了多层含气层系。天然气碳同位素分析表明,该区上三叠统须家河组产出的部分天然气乙烷碳同位素具有明显偏负的特征,相关图版的判别显示,这部分天然气具有原油裂解气的性质。同时在研究区上三叠统须家河组储层中发现了大量的储层沥青充填物,通过岩芯观察、显微照片、元素、热解等分析,发现该储层沥青充填物具有多种类型、多种分布形态、边界较为清楚等特征,且这些沥青充填物的反射率较高,尤其是须二段的储层沥青,这一特征与焦沥青的基本特征类似,表现为油藏裂解后残余物的特征,原油裂解气和焦沥青的发现证实了川西坳陷中段须家河组古油藏的存在。在此基础上,通过综合分析生油及裂解条件等,对研究区须家河组古油藏裂解气成藏模式进行了初步探讨,将这一过程分为印支晚期古油藏形成、燕山中期古油藏裂解、燕山晚期-喜山期气藏调整三个连续的阶段,这对深化认识川西坳陷中段天然气的成因和分布具有一定的意义。     

川东宣汉地区天然气地球化学特征及成因

依据10余口探井60多个气样的化学成份和碳同位素组成数据,结合烃源岩和储层沥青分析资料,系统剖析了四川盆地东部宣汉地区普光、毛坝场等构造带天然气地球化学特征,并探讨了其成因及来源。研究结果表明:这些构造带中飞仙关组—长兴组天然气为高含硫化氢的干气,天然气化学成份表现出古油藏原油裂解气的特点。其烃类气体中以甲烷为主(高于99.5%);富含非烃气体,CO₂和H₂S平均含量分别达5.32%和11.95%。甲烷碳同位素较重(-33‰～-29‰),表征高热演化性质;乙烷δ¹³C值主要分布在-33‰至-28‰范围,属油型气。这些天然气与川东邻近气田的同层位天然气具有同源性,而与石炭系气藏天然气在化学成份、碳同位素组成上有所不同,意味着有不同的气源。硫化物硫同位素和沥青元素组成证实高含量的H₂S是气藏发生TSR作用所致。δ³⁴S值表征层状沉积成因的硬石膏是TSR作用的反应物,而脉状硬石膏则是其残余物。储层的孔隙类型可能与TSR作用强度和H₂S含量高低有联系,裂缝型气层中H₂S少,孔洞型储层中H₂S丰富。乙烷、沥青和各层系烃源岩干酪根碳同位素对比表明研究区飞仙关组—长兴组气藏天然气主要来自二叠系烃源层。     

Accumulation Mechanisms and Evolution History of the Giant Puguang Gas Field,Sichuan Basin,China

Solid bitumens were found throughout the carbonate reservoirs in the Puguang gas field, the largest gas field so far found in marine carbonates in China, confirming that the Puguang gas field evolved from a paleo-oil reservoir. The fluid conduit system at the time of intensive oil accumulation in the field was reconstructed, and petroleum migration pathways were modeled using a 3-D model and traced by geochemical parameters. The forward modeling and inversion tracing coincided with each other and both indicated that oils accumulated in the Puguang-Dongyuezhai structure originated from a generative kitchen to the northwest of the Puguang gas field. The deposition of organic-rich Upper Permian source rocks dominated by sapropelic organic matter in the Northeast Sichuan Basin, the development of fluid conduit system that was vertically near-source rock and laterally near-generative kitchen, and the focusing of oils originated from a large area of the generative kitchen, were the three requirements for the formation of the giant paleo-oil reservoir from which the giant Puguang gas field evolved. The Puguang gas field had experienced a three-stage evolution. The post-accumulation processes, especially the organic-inorganic interaction in the hydrocarbon-water-rock system, had not only profoundly altered the composition and characteristics of the petroleum fluids, but also obviously changed the physicochemical conditions in the reservoir and resulted in complicated precipitation and solution of carbonate minerals.     

四川盆地东部长兴组--飞仙关组气藏地球化学特征及气源探讨

四川盆地上二叠统长兴组生物礁和下三叠统飞仙关组鲕滩是“九五”期间的勘探重点,通过对长兴组-飞仙关组气藏的烃源岩、储层沥青和天然气的地球化学研究,确认了上二叠统的滨岸煤系泥岩和海槽相碳酸盐岩为主要烃源岩,长兴组-飞仙关组气藏天然气主要来源于下伏的上二叠统烃源岩,天然气以垂相运移为主,飞仙关组部分气藏天然气中硫化氢含量较高与储层中膏岩层的分布和热硫酸盐还原作用有关,上述这些特征与沉积相带密切相关。     

四川盆地普光大型气田H2S及优质储层形成机理探讨——读马永生教授的“四川盆地普光大型气田的发现与勘探启示”有感

四川盆地普光大型气田的发现刷新了中国海相碳酸盐岩油气田的多项记录：储量规模最大、储层埋藏最深、资源丰度最高，同时也是中国原油裂解气藏规模最大、天然气最于、硫化氢储量最多的气藏；另外它还是中国目前发现的碳酸盐岩储层次生孔隙最发育的气藏。深入研究后发现，普光超大型气藏的形成具有特殊的地质地球化学条件，即充沛的烃源、储层附近发育一定的膏质岩类、储层经历过较大的埋深〈较高的温度），这些条件是硫酸盐热化学还原作用（thermochemical sulfate reduction，简称TSR，）发生所必须具备的；而正是由于TSR的发生，一方面形成了富含H2S、CO2等酸性气体的流体；同时TSR过程及其形成的硫化氢等酸性流体具有腐蚀性，对深部碳酸盐岩储层进行强烈的溶蚀改造作用，促进了次生大孔洞的发育和优质储层的形成，因此TSR的发生是普光大型气田形成的关键因素之一。     

四川盆地龙马溪组页岩气储层石英类型与特征

为了解页岩气储层石英类型和特征,以四川盆地龙马溪组页岩为研究对象,对样品进行了薄片观察、氩离子抛光-场发射环境扫描电镜观察、能谱分析、X-射线衍射分析、有机碳含量测试。结果表明,龙马溪组页岩石英含量在23%~83%之间,平均值为52%。根据成因,可分为5类:陆源碎屑石英、生物骨骼相关石英、沉积期-成岩早期混合石英、成岩期自生石英和裂缝中石英脉。石英含量与有机碳含量成正相关,其中有机石英在还原环境下能更好地指示有机质的发育情况。有机石英是指保留有软体并演化成干酪根的生物骨骼石英、交代生物骨架石英和与沥青伴生石英。与沥青伴生石英堆积在页岩原生孔隙中,降低了储层的孔隙度,但在一定程度上抑制了后期成岩作用,为沥青的充注保留了空间,且石英与沥青之间发育的缝隙与有机孔一起形成连通的孔隙网络。     

Main Controlling Factors on Hydrocarbon Accumulation and Distribution in Marine Sedimentary Sequences in South China

Multiple source rock assemblages were deposited in the sedimentary provinces in South China in geologic history,and some of them were destructed by and some survived against multiple tectonic movements.Therefore,multiple sources,mixed sources,and uneven distribution of sources occurred in the marine sedimentary basins in South China during the late stage of hydrocarbon pooling.Epidiagenesis of the marine carbonate reservoirs and its modification to reservoir poroperm characteristics determined the formation and the scale of natural gas pools.The exploration practices show that the large to medium gas fields mainly occur in areas with high-quality reservoirs.Detailed study of the paleo-oil accumulations and typical oil and gas reservoirs reveals that the basins experienced multiphase superimposition and modification,leading to the distribution of the Paleozoic paleo-oil accumulations and bitumen in the peripheral areas.The phenomenon that oil and gas production concentrates in the Sichuan basin indicates that the overall sealing conditions of a basin determine the oil/gas potentials and the scale of oil and gas production.This is a critical factor controlling the accumulation and distribution of gas in the marine sequences in South China.The early oil and gas pools in the Yangtze platform left billions of bitumen in the peripheral areas due to the destruction of seals.Since the Himalayan,"late-generation and late-accumulation" gas pools represented by the gas pools in the Sichuan (四川) basin were formed in the marine sedimentary sequences in South China as a result of the change of the sealing conditions.Current gas discoveries appear to be "paleo-generation and paleo-accumulation" gas pools but actually are "late-generation and late-accumulation" gas pools.These patterns of hydrocarbon pooling clearly depict themselves in western Sichuan basin and Weiyuan (威远)gas field.It is revealed that the gas pools in the Sichuan basin were mainly formed as a result of hydrocarbon phase change (thermal cracking of oil to gas),miscible migration,and dynamic equilibration since the Himalayan.A large number of gas pools were formed in the Himalayan and the gas pools in the marine sequences are characterized by late pooling; this kind of gas fields/pools are controlled by:(1) effectiveness of modification and superimposition of the marine basins,(2) effectiveness of the source rocks,(3) effectiveness of the overall preservation conditions,and (4) effectiveness of plays.     

Three Episodes of Hydrocarbon Generation and Accumulation of Marine Carbonate Strata in Eastern Sichuan Basin, China

It is concluded that there are three hydrocarbon generation and accumulation processes in northeastern Sichuan on the basis of the characteristics of solid bitumen, gas-light oils-heavy oils, homogenization temperature of fluid inclusions and diagenesis for beach- and reef-facies dolomite gas- bearing reservoirs in the Puguang Gas Field, northeastern Sichuan Basin, southern China. The first hydrocarbon generation and accumulation episode occurred in the Indosinian movement （late Middle Triassic）. The sapropelic source rocks of the O3w （Upper Ordovician Wufeng Formation）-S1l （Lower Silurian Longmaxi Formation） were buried at depths of 2500 m to 3000 m with the paleogeothermal temperature ranging from 70℃ to 95℃, which yielded heavy oil with lower maturity. At the same time, intercrystalline pores, framework pores and corrosion caused by organic acid were formed within the organic reef facies of P2ch （Upper Permian Changxing Formation）. And the first stage of hydrocarbon reservoir occurred, the level of surface porosity of residual solid bitumen {solid bitumen/ （solid bitumen ＋ residual porosity）} was higher than 60%. The second episode occurred during the Middle Yanshanian movement （late Middle Jurassic）. During that period, the mixed organic source rocks were deposited in an intra-platform sag during the Permian and sapropelic source rocks of O3w-S1l experienced a peak stage of crude oil or light oil and gas generation because they were buried at depths of 3500 m to 6800 m with paleogeothermal temperatures of 96-168℃. At that time, the level of surface porosity of residual solid bitumen of the T1f shoal facies reservoirs was between 25% and 35%, and the homogenization temperatures of the first and second stages of fluid inclusions varied from 100℃ to 150℃. The third episode occurred during the Late Yanshanian （Late Cretaceous） to the Himalayan movement. The hydrocarbon reservoirs formed during the T1f and P2ch had the deepest burial of 7700 m to 8700 m and paleogeotemperatu     

A preliminary evaluation model for reservoir hydrocarbon generating potential established based on dissolved hydrocarbons in oilfield water

OILFIELDWATER,WHICHEXISTSCONCOMITANTLYWITH OILORGASINSUBSURFACERESERVOIRS,ISAKINDOFIMPOR TANTCOMPONENTOFRESERVOIRFLUIDANDALSOISADRIVING FORCEANDCARRIERFORHYDROCARBONMIGRATION,ACCUMULA TIONANDHYDROCARBONRESERVOIRFORMATION.OILFIELDWA TER,HYDROCARBONANDRESER…     

Residual oil as a tool in migration and filling history analysis of petroleum reservoirs,Ghazal Field,Saudi Arabia

Stepwise extraction and molecular analysis of non-recoverable oil from intact reservoir core plugs is used to provide constraints on the accumulation history of petroleum in the Permo-Carboniferous Unayzah reservoirs at the Ghazal Field, Saudi Arabia. When integrated with existing tools such as oil geochemistry, gas geochemistry, stable carbon isotopes, fluid inclusions and thermal modeling, the sequential extraction approach helped decode a previously unrecognized component of the hydrocarbon accumulation history. In particular, it indicates that the region received early petroleum charges that were less mature than currently produced light oil and gas condensates, possibly from the prolific Early Silurian Qusaiba shale source rock and other sources. This has significant implications for prospecting for additional oil, particularly in the north/northwest of the Ghazal region where paleo-oil accumulations may have been displaced or spilled. The lower portion of the Unayzah reservoir (Unayzah-C) remained water-wet during early filling of the upper reservoir unit (Unayzah-A) and appears to have been filled only by a late oil charge. Anomalous molecular and carbon isotopic behavior of residual oil extracts from the uppermost segment of the Unayzah reservoir, where the free oil (first of the sequential extracts) is less mature (0.95% Rc) and isotopically lighter (δ¹³C?31.15‰) than the adsorbed oil (last sequential extract, 1.05% Rc; δ¹³C?29.65‰), suggests a late oil contribution or bitumen contamination from the overlying Khuff Formation.     

贵州仁怀县震旦系灯影组古油藏成藏条件 及油气地质意义

野外观察和研究表明,贵州仁怀县震旦系灯影组古油藏储层为一套碳酸盐台内浅滩环境沉积,主要岩性为砂屑云岩、鲕粒云岩、藻屑云岩和细晶云岩,沥青充填于白云岩晶间孔、粒间孔及岩石溶蚀孔洞内,呈黑色固态物质产出。固体沥青呈块状,质地坚硬,有污手性,镜下观察沥青具中间相结构和镶嵌状结构特征,实测沥青反射率为2.95%~3.86%,双反射明显,热演化程度高,显示储层在地质历史时期曾经遭受高温热演化作用。区域地质及沉积相分析认为,灯影组沉积晚期在上扬子地区存在一个边缘浅滩,并可能存在若干碳酸盐台内浅滩,这种沉积格局控制了滩相储层的发育与展布,震旦纪末期桐湾运动形成的古暴露对该套滩相沉积的颗粒云岩进行溶蚀改造,形成大量孔洞缝,并形成有利的储集体。震旦系陡山沱组和下寒武统牛蹄塘组黑色页岩有机质丰度高、类型好,烃源岩的发育为古油藏的形成提供了丰富的物质基础,下寒武统巨厚的泥页岩组合为油气藏的形成提供了得天独厚的封盖条件,形成了良好的生储盖组合,灯影组和牛蹄塘组之间的不整合面提供了油气运移的通道,加里东运动早期黔中隆起的形成为油气聚集创造了条件。     

桂中坳陷早石炭世泥页岩地球化学特征及近源气成藏模式

目前针对桂中坳陷早石炭世富有机质泥页岩的生烃潜力方面研究很少,严重制约了该区以页岩气为主的非常规油气勘探.本研究对鹿寨县城西石炭系鹿寨组泥页岩系统取样分析,从有机碳含量、岩石热解、有机碳同位素组成、抽提物正构烷烃组成特征及泥岩镜质体反射率多个方面讨论了该套泥页岩的生烃潜力;结合区域构造演化史总结了与下石炭统岩关阶泥页岩密切相关的3种近源气藏赋存模式.研究结果表明:泥页岩的TOC值分布于0.25%~15.67%,其中强制海退前沉积的泥页岩富含有机质,TOC值均大于2%,TOC值与氯仿沥青"A"、生烃潜量及总烃呈弱正相关关系.泥页岩的有机质类型主体为Ⅱ型;泥页岩的R_o值分布于1.72%~2.78%,处于过成熟阶段.泥页岩上下岩性组合特征及桂中坳陷现今所处的构造位置表明,坳陷中部对冲构造区为有利的近源气藏形成区,背冲构造区为较差区;坳陷边缘逆冲推覆构造区为存在岩性圈闭的近源气藏形成区.      

塔河油田、普光气田碳酸盐岩储层特征对比研究

中国海相碳酸盐岩油气勘探相继发现了以塔里木盆地塔河油田、四川盆地普光气田为代表的一批大中型油气田。本文系统对比了塔河油田、普光气田碳酸盐岩储层基本特征、成岩作用和控制因素。礁滩型储层一般物性较好,储集类型为孔隙型或裂缝-孔隙型,非均质性弱;风化壳岩溶型储层一般物性较差,储集类型多样,非均质性极强。白云石化是超深层（〉6000m）碳酸盐岩储层形成的重要机制,白云岩较灰岩储层平均孔隙度可提高3．5％～4．0％。硫酸盐热化学还原（TSR）反应主要是对储层进行强烈改造,改善程度并不大。沉积相、构造作用对不同类型储层的影响程度、影响方式不尽一致：对于风化壳岩溶型储层,沉积相的影响主要体现在对岩石可溶性、透水性的控制上,在岩石可溶、透水的基础上构造作用控制了储层的发育范围及程度;礁滩型储层受沉积相的严格控制,构造作用形成的裂缝对储层物性有明显改善。